Obesity and inactivity are major lifestyle-related epidemics with staggering costs in lives/disability/illness and dollars. As with all epidemics, we have not yet found a way to effectively deal with the problem-either through research or clinical/practical approaches. In this case, quantitative measurement of the energy expenditure (EE) side of energy balance is necessary to effectively investigate the relationship between physical activity (PA) and health, as well as to help people measure their own EE to meet their energy balance goals for weight management. Accelerometry (ACC) is one of the most commonly used methods for assessing EE. However, the body of research indicates that the accuracy of the current generation of ACC has substantial room for improvement (R2~0.50 for free-living PA and R2~0.65 for locomotion) and is insensitive to grade and load. Consequently, we propose a next-generation ACC method and three specific applications of this method. Our method, stride-based ACC, focuses on locomotion: where current ACC measures only magnitude, our method measures ACC pattern (magnitude, duration and shape); and where current ACC relies on group- based calibrations, our method incorporates individual calibration for speed and exploits the strong relationship between speed and EE. Living Systems, Inc. (LSI) has developed, patented, and analyzed substantial preliminary data on stride-based ACC which serves as an enabling technology for three significant PA assessment tools that could overcome the limitations of current ACC: 1) precise tracking of walking EE for weight-management programs, 2) individual calibration for dual-sensor (ACC+HR) monitors that are well- suited to tracking free-living PA, and 3) protocol-free, submaximal assessment of cardiorespiratory fitness -an objective and reproducible measure of recent PA. The overall goal of this multi-phase SBIR project is to apply our stride-based ACC to develop, validate, prototype and commercialize these three PA assessment tools. This goal ideally suits the NCRR mission by advancing state-of-the-art technologies and instruments for research and clinical treatment of health issues. Phase I of the project is focused on demonstrating the feasibility of improving EE accuracy for walking through stride-based ACC for sedentary and overweight/obese subjects, e.g., those most at risk from the inactivity/obesity epidemics. Phase I success will lead to a Phase II effort to develop and validate the three PA assessment applications. Phase I Aims are to: 1) demonstrate accurate/reliable individual calibration for walking speed with success criteria of accuracy of R2>0.90 and test- retest reliability in calibration of R2 >0.90), and 2) demonstrate superior accuracy in estimating EE for walking vs. typical ACC methods with a success criterion of R2 >0.80. During Phase I, subjects will be instrumented with our device and a common activity monitor and gas-exchange indirect calorimetry will be the criterion for EE. We expect Phase II to include field evaluations of accuracy/user satisfaction for each application that will allow us to attract industrial partners and/or private-sector investors for Phase III. Obesity and inactivity are major lifestyle-related epidemics facing our nation. The proposed multi-phase SBIR project titled "New Accelerometry Method for Energy Expenditure and Fitness Assessment Devices" is designed to result in new tools to help researchers understand the relationship between physical activity and health and to help individuals meet their own energy balance goals. [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable]